Resistance training is a form of exercise or therapy where physical resistance against muscle movement is used to strengthen and build muscle. Resistance training benefits overall health and is the basis of many forms of rehabilitation and athletic training. For example, resistance training is often used to rebuild atrophied muscles and restore functionality of strained or injured joints. The muscles of the pelvis and lower extremities include the quadriceps and gluteus maximus, as well as numerous other thigh, leg, ankle, and foot muscles that are used in walking, running, standing, and stability. Traditional devices focused on these muscles include the leg press and other fixed-weight devices. However, such devices typically operate on both legs at the same time and thus are unsuitable in situations where rehabilitation of one leg is desired. In addition, fixed-weight devices provide fixed resistance and are incapable of maximizing resistance across the range of motion of a user's legs. Further, fixed-weight devices commonly have limited or no resistance adjustability. It would therefore be beneficial to provide a device that overcomes the shortcomings of the prior art.